Purpose Nowadays, ionic liquids (ILs) are used as lubricant additives because of their ability to improve tribological characteristics. However, majority of the ILs contains halogen-based anions. They are extremely sensitive to moisture and produce detrimental halides and halogen acids when reacted with moisture and water. These halides and halogen acids are harmful to the health and environment of the operator’s. This paper aims to study four different lubricants including two halogen-based ILs blended in canola oil and two phosphonium-based halogen-free ILs blended in canola oil and in pure canola oil. Design/methodology/approach Viscosity and contact angle were measured by using rheometer and contact angle goniometer, respectively. Machining experiments were performed using turning centre with four different lubricants at two different cutting speeds and temperatures, and the machining forces, tool morphology and roughness of the machined surface were analysed. Findings The results showed that the inclusion of 1% phosphonium-based halogen-free ILs blended in canola oil increased the viscosity by 44.8% and reduced the cutting and thrust force by 21.7% and 26.8%, respectively, compared to pure canola oil lubricant. Microscopic analysis of tool showed lower adhesive and abrasive wear when machined with phosphonium-based halogen-free ILs blended in canola oil. The workpiece surface roughness reduced by 32% for phosphonium-based halogen-free ILs blended in canola oil compared with pure canola oil. Originality/value Halogen-free ILs are possible green lubricants, as they do not contain harmful elements such as F, S, B and Cl like halogen-based ILs. To the best of the authors’ knowledge, this is presumably the first work which shows machining performance of halogen-free ILs as lubricant additives.

No abstract

In recent years, ionic liquids have shown great potential as an additive in lubricants. However, most of the explored ionic liquids for machining applications contain halogen-based anions, which are sensitive to moisture and have a tendency to produce harmful halogen acids (HX) after reacting with water/moisture. These acids are harmful to the environment and can corrode the working surfaces. This study investigates the effectiveness of halogen-free ionic liquids as potential additives to vegetable oil (canola oil). Two halogen-based ionic liquids (1-methyl 3-butylimidazolium tetrafluoroborate [BMIM BF4] and 1-methyl 3-butylimidazolium hexafluorophosphate [BMIM PF6]) and one halogen-free ionic liquids (trihexyl tetradecyl phosphonium bis (24,4-trimethylpentyl) phosphinate P6,6,6,14 [i(C8)2PO2]) were blended individually with canola oil. The percentage ratio of ionic liquid to canola oil is 1:99. Dynamic viscosity and contact angles of different lubricants were measured. Sliding tests were conducted in various conditions; dry, canola oil, and three different blends of ionic liquid with canola oil. Further, to connect tool-chip tribology with machining, turning experiments were carried out under similar lubricating conditions. Results show that the sliding friction, pin surface temperature, and wear were reduced by 48.1%, 44%, and 69.6%, respectively, due to better lubricating ability and spreading tendency of halogen-free ionic liquid blended with canola oil. The microscopic analyses of pin surfaces and the morphology of counter disc surfaces further supported better lubrication between the sliding pair. For P6,6,6,14 [i(C8)2PO2] ionic liquid blended with canola oil, the average cutting temperature and machined workpiece surface roughness reduces by 43.6% and 62.4% compared to dry machining.

No abstract

No abstract